The rules are
X + NA = X NA + NA = NA
sum_na <- function(x,y){
nas <- is.na(c(x,y))
all_na <- all(nas)
any_na <- any(nas)
no_na <- all(!is.na(c(x,y)))
if (all_na) {
return(NA)
} else if (any_na) {
c(x,y)[!nas]
} else if (no_na){
sum(x,y)
}
}
sum_na(1,2)
#> [1] 3
sum_na(1, NA)
#> [1] 1
sum_na(NA, 1)
#> [1] 1
sum_na(NA, NA)
#> [1] NACreated on 2021-05-11 by the reprex package (v2.0.0)
Session info
sessioninfo::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#> setting value
#> version R version 4.0.5 (2021-03-31)
#> os macOS Big Sur 10.16
#> system x86_64, darwin17.0
#> ui X11
#> language (EN)
#> collate en_AU.UTF-8
#> ctype en_AU.UTF-8
#> tz Australia/Perth
#> date 2021-05-11
#>
#> ─ Packages ───────────────────────────────────────────────────────────────────
#> package * version date lib source
#> backports 1.2.1 2020-12-09 [1] standard (@1.2.1)
#> cli 2.5.0 2021-04-26 [1] CRAN (R 4.0.2)
#> crayon 1.4.1 2021-02-08 [1] CRAN (R 4.0.2)
#> digest 0.6.27 2020-10-24 [1] standard (@0.6.27)
#> ellipsis 0.3.1 2020-05-15 [1] standard (@0.3.1)
#> evaluate 0.14 2019-05-28 [1] standard (@0.14)
#> fansi 0.4.2 2021-01-15 [1] CRAN (R 4.0.2)
#> fs 1.5.0 2020-07-31 [1] standard (@1.5.0)
#> glue 1.4.2 2020-08-27 [1] standard (@1.4.2)
#> highr 0.8 2019-03-20 [1] standard (@0.8)
#> htmltools 0.5.1.1 2021-01-22 [1] CRAN (R 4.0.2)
#> knitr 1.31 2021-01-27 [1] CRAN (R 4.0.2)
#> lifecycle 1.0.0 2021-02-15 [1] CRAN (R 4.0.2)
#> magrittr 2.0.1 2020-11-17 [1] standard (@2.0.1)
#> pillar 1.6.0 2021-04-13 [1] CRAN (R 4.0.2)
#> pkgconfig 2.0.3 2019-09-22 [1] standard (@2.0.3)
#> purrr 0.3.4 2020-04-17 [1] standard (@0.3.4)
#> reprex 2.0.0 2021-04-02 [1] CRAN (R 4.0.2)
#> rlang 0.4.11 2021-04-30 [1] CRAN (R 4.0.2)
#> rmarkdown 2.7 2021-02-19 [1] CRAN (R 4.0.2)
#> sessioninfo 1.1.1 2018-11-05 [1] standard (@1.1.1)
#> stringi 1.5.3 2020-09-09 [1] standard (@1.5.3)
#> stringr 1.4.0 2019-02-10 [1] standard (@1.4.0)
#> styler 1.4.1 2021-03-30 [1] CRAN (R 4.0.2)
#> tibble 3.1.1 2021-04-18 [1] CRAN (R 4.0.3)
#> utf8 1.2.1 2021-03-12 [1] CRAN (R 4.0.2)
#> vctrs 0.3.8 2021-04-29 [1] CRAN (R 4.0.2)
#> withr 2.4.2 2021-04-18 [1] CRAN (R 4.0.3)
#> xfun 0.22 2021-03-11 [1] CRAN (R 4.0.2)
#> yaml 2.2.1 2020-02-01 [1] standard (@2.2.1)
#>
#> [1] /Library/Frameworks/R.framework/Versions/4.0/Resources/library